Also you could try upgrading your ram, this boosts up your speed.. ( recommended ram : Crucial or Kingston)

Also,

One of the most common causes of OS X slow-down is the result of an abundance of stored temporary files, namely overflowing system, user and font caches. A relatively simply Terminal commands can clear them out:

atsutil databases -remove

will flush those pesky font buildup, but there are an array of third-party apps (including the two linked above) to help you here, too.

Widgets on dashboard

Close all your widgets if you dont use them, this increases the speed of your MBA

1. Keep a good backup
2. Try and keep ay least 10% free disk space
3. Grab Onyx (selecting the appropriate version depending on which version of OSX you have. Install and run everything on the Automation tab. Maybe do this once a month.
4. Minimise the number of extra tools and apps you have loading to your menu bar.

If you're having specific issues please post further details including which MacBook Air you have, which version of OSX and the problems you're encountering

External hard disk acquisition addict - but admitting the problem is the first step to a robust backupPlease use the reputation system if you think you've been helped - top right of this post